Project Summary Across South Africa and other high-burden settings, rapid expansion in access to antiretroviral therapy (ART) has contributed to major reductions in mother-to-child HIV transmission, but young HIV+ pregnant and postpartum women (PPW) continue to be at highest risk for disengagement from care and suboptimal ART adherence globally. Young HIV+ women experience high levels of stigma related to HIV as well as linked to unintended pregnancy, mental health problems, and alcohol and/or substance use. These intersectional stigmas contribute to poor ART outcomes. Although peer support may improve engagement in care and ART adherence, there are few peer support interventions specifically for young HIV+ PPW. Here we propose a project to develop preliminary data for future evaluations of a peer support intervention that can mitigate the effects of stigma in young HIV+ PPW. This project includes: (i) in-depth interviews with 20 young HIV+ PPW aged 16-24 years to understand how stigma manifests in their lives, and the different forms of peer support that may best mitigate this; (ii) the adaptation of materials into a peer support intervention, with a mobile health (mHealth) platform used as an adjunct for additional support; and (iii) a pilot study of the intervention to mitigate the impact of stigma among young HIV+ PPW aged 16-24 years. The pilot study will include parallel cohorts of pregnant (n=60) and postpartum (n=60) women recruited from a large primary care facility in Gugulethu in Cape Town, South Africa. Women will be randomly allocated to either the peer support intervention or existing standard of care (control) with follow-up for at least 6 months, and engagement in care and viral suppression outcomes will be abstracted from routine medical records. In-depth interviews at exit from the study will be conducted with a subset of 20 women allocated to the intervention. Analyses will explore process outcomes and the impact of the intervention on social support as well as ART outcomes. This project addresses directly the urgent need for innovative interventions to mitigate the impact of stigma in this vulnerable and neglected population, and as such addresses a priority area for NIH research.